In recent years, patients who suffer from atopic dermatitis or sensitive skin and have bad prognosis, the atopic dermatitis or sensitive skin being possibly caused by, for example, remarkable westernization in diet habits and rapid increase in social stress, have increased rapidly. In many cases, the skin inflammations (atopic skin inflammation or the like) of those patients are not adequately treated by treatments with anti-inflammatory skin medicines for external use or anti-inflammatory quasi drugs that have been conventionally used.
For such inflammations, in some cases, cosmetics in which polyalcohols that are general-purpose materials for cosmetics are richly incorporated are more effective than the anti-inflammatory skin medicines for external use or anti-inflammatory quasi drugs, or medical agents for other purposes such as 5-HT antagonist are effective (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).
However, an agent having an effect to adequately treat atopic skin inflammation or the like has not been found yet. Therefore, many atopic skin inflammations are palliatively treated by a combination of external administration of a steroid anti-inflammatory agent such as dexamethasone or prednisolone with an immunosuppressive agent such as cyclosporine, antioxidant such as ascorbic acid, or 5-HT antagonist, and patients suffering from atopic skin inflammations are forced to resist the disadvantages. Accordingly, it has been desired to develop a preparation to prevent inflammation for external use that sufficiently exerts its effect for atopic dermatitis or the like even if the preparation is independently used.
Moreover, it has been feared that those preparations have side effects such as contamination in affected areas by bacteria and ultraviolet hazard, and there has been a problem in use of them for treating atopic skin inflammations over a long period of time.
The above-described conventional therapeutic agents for atopic skin inflammations are agents for treating developed atopic skin inflammations. Meanwhile, means for effectively preventing onset of atopic skin inflammations have not been known. In general, it is known that alleviations of developed inflammations are difficult, and it is significant to provide an agent capable of preventing onset of atopic skin inflammations.
Meanwhile, it is believed that an external skin agent that lowers a representative value for moisture retention such as water loss value is effective for a general skin inflammation. It is published that there is also correlation between an atopic skin inflammation and the water loss value (Non-Patent Document 1). However, the therapeutic effect of the external skin agents that lowers a representative value for moisture retention such as water loss value to the atopic skin inflammation is low. Therefore, it has been desired to develop an external skin agent that has functional mechanism different from those of conventional skin preparations for external use.
It is known that a polymer including a group similar to phosphorylcholine that is one of a structure similar to a biological component is included in an anti-inflammatory external skin agent together with an anti-inflammatory medicine before use (see, for example, Patent Document 4). The anti-inflammatory external skin agent is known to have effects to impair moisture-retention ability to skin and be low irritant to skin.
It is known that when bentonite is included in an inflammatory external skin agent, a system of the inflammatory external skin agent may be stabilized (see, for example, Patent Document 5).
Meanwhile, it is known that when organically modified bentonite is included in an oil cosmetic, it may act as a thickener in an oil phase (see, for example, Patent Document 6).    [Patent Document 1] JP-A-2003-95956    [Patent Document 2] JP-A-08-217695    [Patent Document 3] JP-A-2001-48721    [Patent Document 4] JP-A-2003-26608    [Patent Document 5] JP-A-2003-113069    [Patent Document 6] JP-A-2003-26529    [Non-Patent Document 1] Watanabe, M., Tagami, H., Horii, I., Takahashi, M., Kligman, A. M. Functional analyses of the superficial stratum corneum in atopic xerosis. Arch. Dermatol. 127, 1689-1692, 1991